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        <p>Library Version 11.2.5.3</p>
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          <th colspan="3" align="center">DbEnv::lock_vec()</th>
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          <td width="20%" align="left"><a accesskey="p" href="lockstat_print.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 7. 
                The DbLock Handle
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    <div class="sect1" lang="en" xml:lang="en">
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          <div>
            <h2 class="title" style="clear: both"><a id="lockvec"></a>DbEnv::lock_vec()</h2>
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      <pre class="programlisting">#include &lt;db_cxx.h&gt;
 
int
DbEnv::lock_vec(u_int32_t locker, u_int32_t flags,
    DB_LOCKREQ list[], int nlist, DB_LOCKREQ **elistp);</pre>
      <p>
         The <code class="methodname">DbEnv::lock_vec()</code> method atomically obtains and releases one or
         more locks from the lock table.  The <code class="methodname">DbEnv::lock_vec()</code> method is
         intended to support acquisition or trading of multiple locks under one
         lock table semaphore, as is needed for lock coupling or in
         multigranularity locking for lock escalation.
    </p>
      <p>
         If any of the requested locks cannot be acquired, or any of the locks
         to be released cannot be released, the operations before the failing
         operation are guaranteed to have completed successfully, and
         <code class="methodname">DbEnv::lock_vec()</code> returns a non-zero value.  In addition, if
         <span class="bold"><strong>elistp</strong></span> is not NULL, it is set to
         point to the DB_LOCKREQ entry that was being processed when the error
         occurred.
    </p>
      <p>
         Unless otherwise specified, the <code class="methodname">DbEnv::lock_vec()</code> <span>
            
            <span>
                method either returns a non-zero error value or throws an
                exception that encapsulates a non-zero error value on
                failure, and returns 0 on success.
            </span>
        </span>
    </p>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8171712"></a>Parameters</h3>
            </div>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8183208"></a>locker</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>locker</strong></span> parameter is an unsigned
                          32-bit integer quantity.  It represents the entity requesting or
                          releasing the lock.
                     </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8164768"></a>flags</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
                          or the following value:
                     </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p><a id="vec_DB_LOCK_NOWAIT"></a>
                  <code class="literal">DB_LOCK_NOWAIT</code>
            </p>
                <p>
                 If a lock cannot be granted because the requested lock conflicts with
                 an existing lock, return DB_LOCK_NOTGRANTED immediately instead of
                 waiting for the lock to become available.  In this case, if non-NULL,
                 <span class="bold"><strong>elistp</strong></span> identifies the request that
                 was not granted.
            </p>
              </li>
            </ul>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8187600"></a>list</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>list</strong></span> array provided to
                          <code class="methodname">DbEnv::lock_vec()</code> is typedef'd as DB_LOCKREQ.
                     </p>
          <p>
                          To ensure compatibility with future releases of Berkeley DB, all
                          fields of the DB_LOCKREQ structure that are not explicitly set should
                          be initialized to 0 before the first time the structure is used.  Do
                          this by declaring the structure external or static, or by calling
                          <span class="bold"><strong>memset</strong></span>(3).
                     </p>
          <p>
                          A DB_LOCKREQ structure has at least the following fields:
                     </p>
          <div class="itemizedlist">
            <ul type="disc">
              <li>
                <p><a id="vec_op"></a>
                 <code class="literal">lockop_t op;</code>
            </p>
                <p>
                 The operation to be performed, which must be set to one of the
                 following values:
            </p>
                <div class="itemizedlist">
                  <ul type="circle">
                    <li>
                      <p><a id="vec_DB_LOCK_GET"></a>
                  <code class="literal">DB_LOCK_GET</code>
            </p>
                      <p>
                 Get the lock defined by the values of the <span class="bold"><strong>mode</strong></span> and <span class="bold"><strong>obj</strong></span>
                 structure fields, for the specified 
                 <span class="bold"><strong>locker</strong></span>.  
                 Upon return from <code class="methodname">DbEnv::lock_vec()</code>,
                 if the <span class="bold"><strong>lock</strong></span> field is non-NULL, a
                 reference to the acquired lock is stored there.  (This reference is
                 invalidated by any call to <code class="methodname">DbEnv::lock_vec()</code> or 
                 <a class="xref" href="lockput.html" title="DbEnv::lock_put()">DbEnv::lock_put()</a>  that releases
                 the lock.)
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_GET_TIMEOUT"></a>
                  <code class="literal">DB_LOCK_GET_TIMEOUT</code>
            </p>
                      <p>
                 Identical to DB_LOCK_GET except that the value in the <span class="bold"><strong>timeout</strong></span> structure field overrides any
                 previously specified timeout value for this lock.  A value of 0 turns
                 off any previously specified timeout.
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_PUT"></a>
                  <code class="literal">DB_LOCK_PUT</code>
            </p>
                      <p>
                 The lock to which the <span class="bold"><strong>lock</strong></span> structure
                 field refers is released. The <span class="bold"><strong>locker</strong></span>
                 parameter, and <span class="bold"><strong>mode</strong></span> and <span class="bold"><strong>obj</strong></span> fields are ignored.
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_PUT_ALL"></a>
                  <code class="literal">DB_LOCK_PUT_ALL</code>
            </p>
                      <p>
                 All locks held by the specified <span class="bold"><strong>locker</strong></span> are released.  The <span class="bold"><strong>lock</strong></span>, <span class="bold"><strong>mode</strong></span>,
                 and <span class="bold"><strong>obj</strong></span> structure fields are ignored.
                  Locks acquired in operations performed by the current call to
                 <code class="methodname">DbEnv::lock_vec()</code> which appear before the DB_LOCK_PUT_ALL operation
                 are released; those acquired in operations appearing after the
                 DB_LOCK_PUT_ALL operation are not released.
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_PUT_OBJ"></a>
                  <code class="literal">DB_LOCK_PUT_OBJ</code>
            </p>
                      <p>
                 All locks held on <span class="bold"><strong>obj</strong></span> are released. 
                 The <span class="bold"><strong>locker</strong></span> parameter and the
                 <span class="bold"><strong>lock</strong></span> and <span class="bold"><strong>mode</strong></span> structure fields are ignored.  Locks
                 acquired in operations performed by the current call to
                 <code class="methodname">DbEnv::lock_vec()</code> that appear before the DB_LOCK_PUT_OBJ operation
                 are released; those acquired in operations appearing after the
                 DB_LOCK_PUT_OBJ operation are not released.
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_TIMEOUT"></a>
                  <code class="literal">DB_LOCK_TIMEOUT</code>
            </p>
                      <p>
                 Cause the specified <span class="bold"><strong>locker</strong></span> to timeout
                 immediately.  If the database environment has not configured automatic
                 deadlock detection, the transaction will timeout the next time
                 deadlock detection is performed.  As transactions acquire locks on
                 behalf of a single locker ID, timing out the locker ID associated with
                 a transaction will time out the transaction itself.
            </p>
                    </li>
                  </ul>
                </div>
              </li>
              <li>
                <p><a id="vec_lock"></a>
                  <code class="literal">DB_LOCK lock;</code>
            </p>
                <p>
                A lock reference.
            </p>
              </li>
              <li>
                <p><a id="vec_mode"></a>
                  <code class="literal">const lockmode_t mode;</code>
            </p>
                <p>
                 The lock mode, used as an index into the environment's lock conflict
                 matrix. When using the default lock conflict matrix, <span class="bold"><strong>mode</strong></span> must be set to one of the following
                 values:
            </p>
                <div class="itemizedlist">
                  <ul type="circle">
                    <li>
                      <p><a id="vec_DB_LOCK_READ"></a>
                  <code class="literal">DB_LOCK_READ</code>
            </p>
                      <p>
                read (shared)
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_WRITE"></a>
                  <code class="literal">DB_LOCK_WRITE</code>
            </p>
                      <p>
                write (exclusive)
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_IWRITE"></a>
                  <code class="literal">DB_LOCK_IWRITE</code>
            </p>
                      <p>
                intention to write (shared)
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_IREAD"></a>
                  <code class="literal">DB_LOCK_IREAD</code>
            </p>
                      <p>
                intention to read (shared)
            </p>
                    </li>
                    <li>
                      <p><a id="vec_DB_LOCK_IWR"></a>
                  <code class="literal">DB_LOCK_IWR</code>
            </p>
                      <p>
                intention to read and write (shared)
            </p>
                    </li>
                  </ul>
                </div>
                <p>
                 See <a class="xref" href="envset_lk_conflicts.html" title="DbEnv::set_lk_conflicts()">DbEnv::set_lk_conflicts()</a> 
                 and <a href="../../programmer_reference/lock_stdmode.html" class="olink">Standard Lock Modes</a>
                 for more information on the lock conflict matrix.
            </p>
              </li>
              <li>
                <p>
                         <span class="bold"><a id="obj"></a><strong>const DBT obj;</strong></span>
                     </p>
                <p>
                         An untyped byte string that specifies the object to be locked or
                         released.  Applications using the locking subsystem directly while
                         also doing locking via the Berkeley DB access methods must take care
                         not to inadvertently lock objects that happen to be equal to the
                         unique file IDs used to lock files.  See 
                         <a href="../../programmer_reference/lock_am_conv.html" class="olink">Access method locking 
                             conventions</a> in the
                         <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.
                     </p>
              </li>
              <li>
                <p>
                         <span class="bold"><strong>u_int32_t timeout;</strong></span>
                </p>
                <p>
                        The lock timeout value.
                </p>
              </li>
            </ul>
          </div>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8223392"></a>nlist</h4>
              </div>
            </div>
          </div>
          <p>
                          The <span class="bold"><strong>nlist</strong></span> parameter specifies the
                          number of elements in the <span class="bold"><strong>list</strong></span> array.
                     </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8224472"></a>elistp</h4>
              </div>
            </div>
          </div>
          <p>
                          If an error occurs, and the <span class="bold"><strong>elistp</strong></span>
                          parameter is non-NULL, it is set to point to the DB_LOCKREQ entry that
                          was being processed when the error occurred.
                     </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8225552"></a>Errors</h3>
            </div>
          </div>
        </div>
        <p>
                         The <code class="methodname">DbEnv::lock_vec()</code> <span>
            
            <span>
                method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a> 
                exception, encapsulating one of the following non-zero errors, or return one
                of the following non-zero errors:
            </span>
        </span>
                    </p>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8193312"></a><span>DbDeadlockException or </span>DB_LOCK_DEADLOCK</h4>
              </div>
            </div>
          </div>
          <p>
                A transactional database environment operation was selected to resolve
                a deadlock.
            </p>
          <p>
                <a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
                your Berkeley DB API is configured to throw exceptions.
                Otherwise, <code class="literal">DB_LOCK_DEADLOCK</code> is returned.
            </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8205440"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
              </div>
            </div>
          </div>
          <p>
                A Berkeley DB Concurrent Data Store database environment configured
                for lock timeouts was unable to grant a lock in the allowed time.
            </p>
          <p>
                You attempted to open a database handle that is configured
                for no waiting exclusive locking, but the exclusive lock could not be
                immediately obtained. See
                <a class="xref" href="dbset_lk_exclusive.html" title="Db::set_lk_exclusive()">Db::set_lk_exclusive()</a>
                for more information.
            </p>
          <p>
                <a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
                your Berkeley DB API is configured to throw exceptions.
                Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
            </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8173592"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
              </div>
            </div>
          </div>
          <p>
                The <a class="link" href="lockvec.html#vec_DB_LOCK_NOWAIT">DB_LOCK_NOWAIT</a>
                flag or lock timers were configured and the lock could not be granted
                before the wait-time expired.
            </p>
          <p>
                <a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
                your Berkeley DB API is configured to throw exceptions.
                Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
            </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8158096"></a>EINVAL</h4>
              </div>
            </div>
          </div>
          <p>
                An invalid flag value or parameter was specified.
            </p>
        </div>
        <div class="sect3" lang="en" xml:lang="en">
          <div class="titlepage">
            <div>
              <div>
                <h4 class="title"><a id="idp8158536"></a>ENOMEM</h4>
              </div>
            </div>
          </div>
          <p>
                The maximum number of locks has been reached.
            </p>
        </div>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8195856"></a>Class</h3>
            </div>
          </div>
        </div>
        <p>
                    <a class="link" href="env.html" title="Chapter 5.  The DbEnv Handle">DbEnv</a>, 
                    <a class="link" href="lock.html" title="Chapter 7.  The DbLock Handle">DbLock</a> 
            </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idp8226528"></a>See Also</h3>
            </div>
          </div>
        </div>
        <p>
                     <a class="xref" href="lock.html#locklist" title="Locking Subsystem and Related Methods">Locking Subsystem and Related Methods</a> 
                </p>
      </div>
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